Method for applying particulate matter to a cable core

ABSTRACT

A method of applying particulate matter to a cable core comprising providing first and second chambers, both of which have entrance and exit ports, the first chamber containing particulate matter and the exit port of the second chamber containing an air wipe which includes a cable core passageway in communication with the interior and exterior of the second chamber and at least one air passageway which is in communication with the cable core passageway and has an elongated longitudinal axis disposed at an acute angle to the longitudinal axis of the cable core passageway so that gas flowing through such a passageway is directed into the second chamber; passing a cable core through the first chamber and applying particulate matter to it to form a coated core; passing the coated core through the second chamber and said air wipe; and, forcing a gas through the air passageway in the air wipe onto the coated core to remove a predetermined amount of particulate matter from the coated core and transmit same into the interior of the second chamber.

This is a division of U.S. Ser. No. 07/322,343, filed Mar. 13, 1989, forMethod and Apparatus for Applying Particulate Matter to a Cable Core.

BACKGROUND OF THE INVENTION

This invention relates to both method and apparatus for applyingparticulate matter to a cable core, such being applicable equally totelecommunications as well as power cable. The cable core can becomposed of electrical energy conducting materials, such as copper oraluminum, or glass fibers for conducting light energy, all of which arereferred to in this disclosure as "conductors", irrespective of whetherthey are intended to conduct light or electrical energy.

The prior art recognizes the desirability of applying to cable corespowdered hydrophylic materials adapted to swell (increase its volume)upon coming in contact with water. See U.S. Pat. No. 4,002,809incorporated herein by reference. Such powder performs two functions:(a) absorbs water that enters the cable; and (b) forms a blockingmechanism to the further entry of water into the cable. Discussion ofthe desirability of such a water blocking agent in a cable is set forthin U.S. Pat. No. 4,100,002, 4,419,157, 4,525,026 and 4,297,624,incorporated herein by reference, for further background.

SUMMARY OF THE INVENTION

As a preferred embodiment, this invention has particular application towater swellable elements used to block the passage of water through acable if the cable should be cut. This aspect is particularly importantin ship and underwater operations, where water type bulkheads are usedto seal the undamaged portions of the vessel from a section of thevessel which has been damaged. It also has particular applications toburied fiber optic cable that comes in constant contact with groundwater. It is important to allow communications cable to remainoperational after water has entered the cable. This goal would becompromised if water could seep through communications cable from thedamaged portion of the vessel or underground cable to the undamagedportion. Therefore, one of the objects of the invention is tolongitudinally water block a cable, so that such water seepage cannottake place.

One example, a preferred embodiment, of the invention employs a fiberoptic cable sub-unit composed of an optical fiber with an outer coatingof polyester circumscribed by a plastic outer jacket. Aramid yarnimpregnated or coated with a water swellable powder, acrylic acid powderfor example, is disposed between the coated optical fiber and the outerjacket. Dusting the yarn with a swellable powder in advance is a usefulmethod of making such a sub-unit. Applicant has found that wheneverthere is an application of water swellable (hydrophylic) powders ofparticulate matter to cable core there are certain problems. Some ofthese problems are recognized in U.S. Pat. No. 4,419,157, incorporatedherein by reference. One problem that is not believed to be recognizedby the prior art is that water swellable particulate matter applied to acable core results in a coated cable core with an irregular surface,i.e., it is not concentric or smooth. See FIG. 2 of this disclosure forexample. The particulate matter coating usually achieved is bumpy andhas numerous irregularities that do not recommend it to subsequentjacketing of the core in a quality manner. This gives rise to theproblem of how to shape particulate matter forming the coating on thecable core without disturbing the main body of the particulate mattercoating to impair its integrity and simultaneously keep the particulatematter contained so that it does not escape to the atmosphere outside ofthe applying apparatus. Applicant has found that these problem can besolved by passing the cable core through first and second chambers andthen through an airwipe that has air passages that direct air andparticulate matter removed from a coated cable core to the interior ofthe second chamber. In the first chamber, which is a rotating chamber,particulate matter is disposed on the bare cable core. Emerging from thefirst chamber is a coated cable core that is irregular in its surfaceand not readily adapted to further jacketing operations in a qualitymanner. See FIG. 2 of this disclosure. Applicant has found that bypassing the coated cable core through a second chamber and an air wipe,this problem can be solved. By providing air passageways in the air wipethat are disposed at an acute angle to the longitudinal axis of thecable core passageway of the air wipe, particulate matter can beconfined to the second chamber.

The exit port of the first chamber is coaxially aligned with theentrance and exit ports of the second chamber. The exit port of thesecond chamber contains an air wipe comprised of a cable core passagewaythat communicates with the interior and exterior of the second chamberand a plurality of air passageways that communicate with the cable corepassage way and lie at an acute angle as above described. Connected tothe air passageways is a source of compressed gas, whose pressure can becontrolled. Using this apparatus, a number of streams of gas (usuallyair) pass through the air passageway, impinge upon the surface of theparticulate matter coated cable core, remove any excess particulatematter from the coated cable core, form a concentric smooth surfaceparticulate matter cable core, and transmit the excess particulatematter to the interior of the second chamber.

After the cable core has been coated and passed through the air wipe, itis then passed to an operation where a cable core wrap or jacket or bothare applied to the coated cable core in a conventional well known priorart manner. See U.S. Pat. No. 4,419,157 for prior art teachings ofcoating a coated cable core.

Applicant is familiar with a prior art mechanism sold under thetrademark Chalkmaster, made by the Warbrick Engineering of Cheshire,England. This apparatus employes a fluidized bed as a powder applicatorfor cables, wires, hose, tubes, and profiles and the advertisement forthis mechanism states that U.K. Patent 2055632B is applicable. Applicanthas found that this one chamber prior art mechanism is expressly adaptedfor the application of "chalk" (calcium carbonate) to an elongatedmember such as a cable core. When hydrophylic powder is used in thisapparatus, instead of chalk, moisture in the air crosses the waterswellable powder to conglomerate, to compact. This causes the amount ofnon-compacted powder to decrease in volume, coating is decreased andthis causes the operator to feed more air into the fluidized bed of theChalkmaster applicator to increase the supply of particulate matter,resulting in almost constant and unwanted adjustments in air feed as thehumidity impacts the particle size distribution of the particulatematter. An air wipe is used by this prior art device; however, air isfed in a stream that is essentially perpendicular to the longitudinalaxis of a cable core and particulate matter coated thereon. As a result,particulate matter is blown not only back into the single chamber wherethe fluidized bed is disposed, but to the outside surroundings as well.Such is dangerous, especially when using hydrophylic powders. Anoperator breathing such powder all day is exposing himself tounnecessary risks. It is to the solution of these two problems that thisinvention is directed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a cable core prior to it being coated withparticulate matter.

FIG. 2 is the cable core of FIG. 1 coated with particulate matter.

FIG. 3 is the coated cable core of FIG. 2 after being passed through theair wipe of the invention.

FIG. 4 is the coated cable core of FIG. 3 circumscribed by a jacket.

FIG. 5 is a side elevation of a partial cross section of the apparatusused to make the coated cable core of FIG. 3.

FIG. 6 is a cross section of the air wipe portion of the apparatus shownin FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 1 as element 1 is a conventional fiber optic cable core,having a central strength member 7 circumscribed by a plastic jacket 8and a plurality of buffer tubes 9, in which there is disposed opticalfibers 10. The buffer tubes are disposed around jacket 8 andcircumscribing the buffer tubes 9 is aramid fibers 11. Element 1 isprior art cable core of conventional design. Optical fibers 10, buffertubes 9 can obviously be replaced with insulated or electricalconductors (not shown) in a manner well known to the prior art.

Shown as element 2 in FIG. 2 is the prior art cable core 1 of FIG. 1coated with particulate matter 12. Element 2 is the element that iscreated by passing cable core 1 through chamber 13 and into chamber 14of FIG. 5 as will be more fully explained at a later time. The prior artcoated cable core of FIG. 2 is irregular in shape because of the unevenapplication of the particulate matter.

Shown in FIG. 3 by element 3 is a cable core coated using the hereindisclosed invention. It will be noted that the coating of particulatematter 12 is concentric and does not contain any irregularities as shownby element 12 of FIG. 2. Element 3 is the product of the hereindisclosed method using the apparatus shown in FIG. 5, as it emerges fromcable core passageway 21 of air wipe 6. Using conventional extrusionapparatus (not shown) element 3 of FIG. 3 is made into a finished cable4 by applying jacket 13 over particulate matter 12.

Turning now to FIG. 5, there is shown element 5, the apparatus used tomake the coated able core 3 of FIG. 3. This apparatus comprises a frame24, on which a first chamber 13 and second chamber 14 are disposed.First chamber 13 is rotatably mounted so that it rotates along itslongitudinal axis and around dies 17 and 15. Motor 25, through drivemechanism 26, rotates first chamber 13. Particulate matter such as acarboxymethylcellulose, bentonite or acrylic acid powder are placed infirst chamber 13. Another example is a powder made by Dow ChemicalCompany, U.S.A. of Midland, Mich., 48674, identified as XUS-40346.00LDevelopmental Powder. Such powders swell upon being brought into contactwith water and are otherwise known as hydrophylic powders.

First chamber 13 has inlet and outlet ports 17 and 18 delimited bysupport members 16 and 15 respectively. Support members 15 and 16support first chamber 13, which rotates about them. Element 23represents means for ingress and egress into the interior of firstchamber 13. Support member 16 circumscribes die 33. Support member 15contains die 34. Anchoring means 19 is affixed to support member 15 tocreate a shoulder against which die 34 abuts so that it is kept in theposition as shown. The cable core, as it exits from chamber 13 andenters support member 15 resembles element 2 but with a larger amount ofparticulate matter on top. Die 34 is used to remove this uppermostexcess and trim the coated cable core to that approximating that shownby element 2 of FIG. 2. The excess then is pushed back into chamber 13.Second chamber 14 is not necessarily a rotatable chamber and has inletport 19, defined by die 15 and exit port 21 as defined by airwipe 6.Second chamber 14 also has an additional port 27 through which excessparticulate matter can be withdrawn by a vacuum, see element 30, as thecoated cable core 2 travels through second chamber 14 and air wipe 6.Vacuum means 30 is connected to port 27 to ducts 31 and 32 and used toremove gas and particulate matter suspended in the gas, usually air.Element 23 represents a value for controlling a supply of compressed airor gas provided by element 35 and conduit 36. Such gas is connected byconduit 37 to air passageways 22 of airwipe 6 to provide a stream of airthrough passageway 22 into passageways 29 where it is allowed to impingeupon and carve or sculpt the particulate matter 12 of FIG. 2. Suchcarving or sculpting results in particulate matter 12 of FIG. 3, aconcentric layer of particulate matter rather than an irregular layer ofparticulate matter as shown by the same element in FIG. 2.

Air passageways 29 have an longitudinal axis disposed at an acute angleto the longitudinal axis of cable core passageway 33 so that air or gasforced through passageway 29 is forced through passageway 33 and intosecond chamber 14, where the particulate matter is either confined insecond chamber 14 or is removed by vacuum means 30 and duct workelements 31 and 32. In this manner, the atmosphere surrounding theapparatus for coating a cable core is essentially free of particulatematter.

In practice, prior art cable core 1 is threaded into die 16 and entersinto the interior of first chamber 13 through port 17. Particulatematter in first chamber 13 is then applied to cable core 1 by therotation of first chamber 13 and particulate matter therein. Thisprocess results in a particulate coated cable core like that shown inelement 2 of FIG. 2. Element 2 is then traversed through port 18, die 15and through port 19 into second chamber 14, thence into port 20 andcable core passageway 21, where one or more streams of air or compressedgas is directed at particulate matter 12 of FIG. 2 to sculpt or carvesame into the concentric configuration shown by element 12 of FIG. 3.Coated cable core 3 of FIG. 3 emerges from port 21 and airwipe 6 to belater processed into a finished cable by placing a jacket 13 thereon byconventional means (not shown). Port 28 is a means to access and removeany excess particulate matter accumulated in chamber 14. This can bedone either by gravity or by vacuum means such as that shown by elements27, 31, 30, and 32.

What is claimed is:
 1. A method of applying particulate matter to acable core comprising:(a) providing first and second chambers, both ofsaid first and second chambers having entrance and exit ports, saidfirst chamber containing particulate matter therein and the exit port ofsaid second chamber comprising an air wipe, said air wipe comprising acable core passageway having a longitudinal axis in communication withthe interior and exterior of said second chamber and at least one airpassageway in communication with said cable core passageway, said airpassageway having an longitudinal axis disposed at an acute angle to thelongitudinal axis of the cable core passageway so that gas forcedthrough said air passageway will be directed into the second chamber;(b) passing a cable core through said first chamber and applyingparticulate material thereto to form a coated core; (c) passing saidcoated core through said second chamber and said air wipe; and, (d)forcing a gas through the air passageway on to said coated core toremove a predetermined amount of particulate matter from said coatedcore.
 2. The method of claim 1, further including the step of rotatingsaid first chamber while passing said cable core therethrough.
 3. Themethod of claim 1 wherein said second chamber contains another exit portfurther including the step of removing gas and particulate matterthrough said another exit port while passing said coated core throughsaid air wipe.
 4. The method of claim 1 wherein said particulate matteris hydrophylic.